1. Field of the Invention
The present invention relates to a method and apparatus for measuring figure of deflection (i.e., deflection characteristics) of a golf club shaft.
2. Description of Related Art
Deflection of a golf club shaft is represented by a bend value which is in turn represented by a maximum displacement (i.e., deflection or elastic deformation) of a tip end (i.e., head end) of a golf club that is measured when a predetermined weight is suspended from the tip of the golf club whose butt end (i.e., grip end) is fixed. Note that, in a tapered rod like a golf club shaft, the larger diameter end is called the butt end and the smaller diameter end the tip end. The deflection decreases as the stiffness of the club shaft increases. Accordingly, the stiffness of the club shaft can be represented by the bend value. The whole figure of deflection of the club shaft cannot, however, be identified by the bend value.
Another parameter of figure of deflection of a golf club is known as a "kick point". This concept has been developed to detect the portion of the club which can be most easily deformed. The kick point is represented, for example, by a ratio of the butt bend value, measured when a weight is suspended from the butt end of the club shaft, to the tip bend value, measured when the weight is suspended from the tip end of the club shaft. A ratio of around 2.3 corresponds to an intermediate kick point. A ratio larger than 2.3 (e.g., around 3.0) corresponds to a tip kick point, and a ratio smaller than 2.3 (e.g., 1.8) corresponds to a butt kick point. However, it is very difficult to intuitively grasp or recognize the numerical values of the various kick points since the kick point values have no dimension, Namely, the kick points values do not represent any length.